Artery occlusion in lower limb due to arteriosclerosis obliterans, Buerger's disease, arterial embolism etc. causes circulatory deficit in legs and toes probably resulting in ulcers and/or necrosis thereof, that is called, severe ischemic limbs. One of reliable therapy for severe ischemic limbs is a bypass surgery to graft an autologous vein to the lower limb artery that has occlusion. An example of such bypass surgery is femoropopliteal artery revascularization.
Patients with arteriosclerosis obliterans recently increase due to aging of population, increase of diabetic patients and dialyzed patients. The increase of patients with severe ischemic limbs that are terminal illnesses of arteriosclerosis obliterans is deeply concerned. However, there is no sufficient number of vascular surgeons that carry out the operation for femoropopliteal artery revascularization.
In femoropopliteal artery revascularization, it is required to bypass the occluded artery from the center (near to heart) to the periphery (far from heart) in order to make blood circulation to periphery over the occluded portion of the artery. For such artery revascularization, a great saphenous vein is autogenously used as the best biomaterial for such bypassing. There are reverse, non-reverse and in-situ treatments for surgical approaches adopted in femoropopliteal artery revascularization.
FIGS. 1A and 1B show blood flow and opening or closing of a venous valve in vein 1. FIGS. 1A and 1B specifically show the opening of a venous valve 2 in the blood flow from the periphery P to the center C and the closing of the venous valve 2 in that from the center C to the periphery P, respectively.
In most cases, arteries exist from the heart to the periphery in parallel to the veins. Arteries have rather thick and elastic blood vessel wall and conduct the artery blood pumped in heartbeat from the heart to the peripheries. On the other hand, vein 1 has less elastic blood vessel wall than artery. The venous blood is pushed back to the heart from the peripheries by opening and closing function of a venous valve 2 and pumping function of muscles in the lower limbs or upper limbs.
The normal venous valve 2 cannot invert opening to the periphery P.
A plurality of venous valves 2 exits in the inner cavity of the vein 1 as shown in FIGS. 1A and 1B. The venous valve 2 is a bileaflet valve and let the blood pass from the peripheries to the center as shown in FIG. 1A. When the blood turns to change the flow orientation as flowing from center to the peripheries, the venous valves 2 close and block such flow orientation of the blood, as shown in FIG. 1B. The center side of the venous valve 2, the intravenous valvular sinus 4 inflates by the blood pressure.
In the reverse treatment, a treatment of those adopted for femoropopliteal artery revascularization, a vein 1 is, as an autologous vein, taken off by cutting it off from a vein staying usually near body surface. Putting it in the center C side in the periphery side, the cut end of the center side of the vein is anastomosed to the periphery side of the occluded portion of the artery and then the cut end of the periphery side of the vein to the center side of the occluded portion of the artery.
In the non-reverse treatment, the vein is not reversely put, as the center C side is put in the periphery side after cutting off and it is anastomosed to the artery over the occluded portion as the center side of the vein is anastomosed to the center side of the occluded portion of the artery and the periphery side to the periphery side of the occluded portion of the artery. The orientation of the harvested vein is same as that of the artery.
In the in-situ treatment, the vein existing close to and in parallel to the artery that has an occlusion is anastomosed thereto as a bypassing blood vessel.
In-situ treatment is superior to the reverse treatment and the non-reverse one in terms of not cutting off from the vein to obtain the grafting vessel. In the actual treatment, the vein close to the artery is cut at the center side and periphery side parallel to those sides of the occluded portion of the artery. The vein is harvested from the original position of the cut portion of the vein 1. The branching vessel 6 that branches from the harvested vein is closed and the harvested vein is anastomosed to the artery at the two cut ends but still staying in parallel to the artery.
In the reverse treatment, the orientation of blood flow in the vessel is unchanged before and after grafting since the vein 1 as cut as an autologous vein 1 (as shown in FIGS. 1A and 1B) is reversely put the center C side to the periphery side. Therefore, the artery blood does not stagnate in the vessel after anastomosing the vein to the artery without cutting venous valves.
However, the veins tend to be generally thicker as closer they are to the heart. Even in case that they have the same diameters in the center C side and the peripheries P side, the portion in the center C has more elastic and stretchable than that in the peripheries P. Therefore, the harvested vein has to be anastomosed to a thick artery in the center C side with the periphery side of the thin portion of the harvested vein and thin artery in the periphery P side with the center side of the thick portion of the harvested vein.
On the other hand, the thick and elastic portion of the vein 1 (that is, the center C side of the vein 1) can be anastomosed to the thick portion of the artery and the thin and less elastic portion of the vein 1 (that is, the periphery P side of vein 1) to the thin portion of the artery in the non-reverse and the in-situ treatments. As the result, the anastomosed vein has the similar taper by nature to the artery as the thicker the closer to the heart.
However the artery blood flow, that is in the orientation from the center C side to the peripheries P, is inverse flow orientation in the vein 1 (an autologous vein). Therefore, the blood flow in the grafted vein (an autologous vein) anastomosed to the artery is blocked by the venous valves 2. To obtain normal blood flow of the grafted vein in non-reverse and in-situ treatments, a treatment to destroy the venous valves 2 in the vein 1 (an autologous vein) is required.